This invention relates generally to devices that produce ozone and an electrokinetic flow of air from which particulate matter has been substantially removed, and more particularly to cleaning the wire or wire-like electrodes present in such devices.
The use of an electric motor to rotate a fan blade to create an air flow has long been known in the art. Unfortunately, such fans produce substantial noise, and can present a hazard to children who may be tempted to poke a finger or a pencil into the moving fan blade. Although such fans can produce substantial air flow, e.g., 1,000 ft3/minute or more, substantial electrical power is required to operate the motor, and essentially no conditioning of the flowing air occurs.
It is known to provide such fans with a HEPA-compliant filter element to remove particulate matter larger than perhaps 0.3 xcexcm. Unfortunately, the resistance to air flow presented by the filter element may require doubling the electric motor size to maintain a desired level of airflow. Further, HEPA-compliant filter elements are expensive, and can represent a substantial portion of the sale price of a HEPA-compliant filter-fan unit. While such filter-fan units can condition the air by removing large particles, particulate matter small enough to pass through the filter element is not removed, including bacteria, for example.
It is also known in the art to produce an air flow using electro-kinetic techniques, by which electrical power is directly converted into a flow of air without mechanically moving components. One such system is described in U.S. Pat. No. 4,789,801 to Lee (1988), depicted herein in simplified form as FIGS. 1A and 1B. Lee""s system 10 includes an array of small area (xe2x80x9cminisectionalxe2x80x9d) electrodes 20 that is spaced-apart symmetrically from an array of larger area (xe2x80x9cmaxisectionalxe2x80x9d) electrodes 30. The positive terminal of a pulse generator 40 that outputs a train of high voltage pulses (e.g., 0 to perhaps +5 KV) is coupled to the minisectional array, and the negative pulse generator terminal is coupled to the maxisectional array.
The high voltage pulses ionize the air between the arrays, and an air flow 50 from the minisectional array toward the maxisectional array results, without requiring any moving parts. Particulate matter 60 in the air is entrained within the airflow 50 and also moves towards the maxisectional electrodes 30. Much of the particulate matter is electrostatically attracted to the surface of the maxisectional electrode array, where it remains, thus conditioning the flow of air exiting system 10. Further, the high voltage field present between the electrode arrays can release ozone into the ambient environment, which appears to destroy or at least alter whatever is entrained in the airflow, including for example, bacteria.
In the embodiment of FIG. 1A, minisectional electrodes 20 are circular in cross-section, having a diameter of about 0.003xe2x80x3 (0.08 mm), whereas the maxisectional electrodes 30 are substantially larger in area and define a xe2x80x9cteardropxe2x80x9d shape in cross-section. The ratio of cross-sectional radii of curvature between the maxisectional and minisectional electrodes is not explicitly stated, but from Lee""s figures appears to exceed 10:1. As shown in FIG. 1A herein, the bulbous front surfaces of the maxisectional electrodes face the minisectional electrodes, and the somewhat sharp trailing edges face the exit direction of the air flow. The xe2x80x9csharpenedxe2x80x9d trailing edges on the maxisectional electrodes apparently promote good electrostatic attachment of particular matter entrained in the airflow. Lee does not disclose how the teardrop shaped maxisectional electrodes are fabricated, but presumably they are produced using a relatively expensive mold-casting or an extrusion process.
In another embodiment shown herein as FIG. 1B, Lee""s maxisectional sectional electrodes 30 are symmetrical and elongated in cross-section. The elongated trailing edges on the maxisectional electrodes provide increased area upon which particulate matter entrained in the airflow can attach. Lee states that precipitation efficiency and desired reduction of anion release into the environment can result from including a passive third array of electrodes 70. Understandably, increasing efficiency by adding a third array of electrodes will contribute to the cost of manufacturing and maintaining the resultant system.
While the electrostatic techniques disclosed by Lee are advantageous over conventional electric fan-filter units, Lee""s maxisectional electrodes are relatively expensive to fabricate. Further, increased filter efficiency beyond what Lee""s embodiments can produce would be advantageous, especially without including a third array of electrodes.
The invention in applicants"" parent application provided a first and second electrode array configuration electro-kinetic air transporter-conditioner having improved efficiency over Lee-type systems, without requiring expensive production techniques to fabricate the electrodes. The condition also permitted user-selection of safe amounts of ozone to be generated.
The second array electrodes were intended to collect particulate matter, and to be user-removable from the transporter-conditioner for regular cleaning to remove such matter from the electrode surfaces. The user must take care, however, to ensure that if the second array electrodes were cleaned with water, that the electrodes are thoroughly dried before reinsertion into the transporter-conditioner unit. If the unit were turned on while moisture from newly cleaned electrodes was allowed to pool within the unit, and moisture wicking could result in high voltage arcing from the first to the second electrode arrays, with possible damage to the unit.
The wire or wire-like electrodes in the first electrode array are less robust than the second array electrodes. (The terms xe2x80x9cwirexe2x80x9d and xe2x80x9cwire-likexe2x80x9d shall be used interchangeably herein to mean an electrode either made from a wire or, if thicker or stiffer than a wire, having the appearance of a wire.) In embodiments in which the first array electrodes were user-removable from the transporter-conditioner unit, care was required during cleaning to prevent excessive force from simply snapping the wire electrodes. But eventually the first array electrodes can accumulate a deposited layer or coating of fine ash-like material.
If this deposit is allowed to accumulate eventually efficiency of the conditioner-transporter will be degraded. Further, for reasons not entirely understood, such deposits can produce an audible oscillation that can be annoying to persons near the conditioner-transporter.
Thus there is a need for a mechanism by a conditioner-transporter unit can be protected against moisture pooling in the unit as a result of user cleaning. Further there is a need for a mechanism by which the wire electrodes in the first electrode array of a conditioner-transporter can be periodically cleaned. Preferably such cleaning mechanism should be straightforward to implement, should not require removal of the first array electrodes from the conditioner-transporter, and should be operable by a user on a periodic basis.
The present invention provides such a method and apparatus.
Applicants"" parent application provides an electro-kinetic system for transporting and conditioning air without moving parts. The air is conditioned in the sense that it is ionized and contains safe amounts of ozone. The electro-kinetic air transporter-conditioner disclosed therein includes a louvered or grilled body that houses an ionizer unit. The ionizer unit includes a high voltage DC inverter that boosts common 110 VAC to high voltage, and a generator that receives the high voltage DC and outputs high voltage pulses of perhaps 10 KV peak-to-peak, although an essentially 100% duty cycle (e.g., high voltage DC) output could be used instead of pulses. The unit also includes an electrode assembly unit comprising first and second spaced-apart arrays of conducting electrodes, the first array and second array being coupled, respectively, preferably to the positive and negative output ports of the high voltage generator.
The electrode assembly preferably is formed using first and second arrays of readily manufacturable electrode configurations. In the embodiments relevant to this present application, the first array included wire (or wire-like) electrodes. The second array comprised xe2x80x9cUxe2x80x9d-shaped or xe2x80x9cLxe2x80x9d-shaped electrodes having one or two trailing surfaces and intentionally large outer surface areas upon which to collect particulate matter in the air. In the preferred embodiments, the ratio between effective radii of curvature of the second array electrodes to the first array electrodes was at least about 20:1.
The high voltage pulses create an electric field between the first and second electrode arrays. This field produces an electro-kinetic airflow going from the first array toward the second array, the airflow being rich in preferably a net surplus of negative ions and in ozone. Ambient air including dust particles and other undesired components (germs, perhaps) enter the housing through the grill or louver openings, and ionized clean air (with ozone) exits through openings on the downstream side of the housing.
The dust and other particulate matter attaches electrostatically to the second array (or collector) electrodes, and the output air is substantially clean of such particulate matter. Further, ozone generated by the transporter-conditioner unit can kill certain types of germs and the like, and also eliminates odors in the output air. Preferably the transporter operates in periodic bursts, and a control permits the user to temporarily increase the high voltage pulse generator output, e.g., to more rapidly eliminate odors in the environment.
Applicants"" parent application provided second array electrode units that were very robust and user-removable from the transporter-conditioner unit for cleaning. These second array electrode units could simply be slid up and out of the transporter-conditioner unit, and wiped clean with a moist cloth, and returned to the unit. However on occasion, if electrode units are returned to the transporter-conditioner unit while still wet (from cleaning), moisture pooling can reduce resistance between the first and second electrode arrays to where high voltage arcing results.
Another problem is that over time the wire electrodes in the first electrode array become dirty and can accumulate a deposited layer or coating of fine ash-like material. This accumulated material on the first array electrodes can eventually reduce ionization efficiency. Further, this accumulated coating can also result in the transporter-conditioner unit producing 500 Hz to 5 KHz audible oscillations that can annoy people in the same room as the unit.
In a first embodiment, the present invention extends one or more thin flexible sheets of Mylar or Kapton type material from the lower portion of the removable second array electrode unit. This sheet or sheets faces the first array electrodes and is nominally in a plane perpendicular to the longitudinal axis of the first and second array electrodes. Such sheet material has high voltage breakdown, high dielectric constant, can withstand high temperature, and is flexible. A slit is cut in the distal edge of this sheet for each first array electrode such that each wire first array electrode fits into a slit in this sheet. Whenever the user removes the second electrode array from the transporter-conditioner unit, the sheet of material is also removed. However in the removal process, the sheet of material is also pulled upward, and friction between the inner slit edge surrounding each wire tends to scrape off any coating on the first array electrode. When the second array electrode unit is reinserted into the transporter-conditioner unit, the slits in the sheet automatically surround the associated first electrode array electrode. Thus, there is an up and down scraping action on the first electrode array electrodes whenever the second array electrode unit is removed from, or simply moved up and down within, the transporter-conditioner unit.
Optionally, upwardly projecting pillars can be disposed on the inner bottom surface of the transporter-conditioner unit to deflect the distal edge of the sheet material upward, away from the first array electrodes when the second array electrode unit is fully inserted. This feature reduces the likelihood of the sheet itself lowering the resistance between the two electrode arrays.
In a presently preferred embodiment, the lower ends of the second array electrodes are mounted to a retainer that includes pivotable arms to which a strip of Mylar or Kapton type material is attached. The distal edge of each strip includes a slit, and the each strip (and the slit therein) is disposed to self-align with an associated wire electrode. A pedestal extends downward from the base of the retainer, and when fully inserted in the transporter-conditioner unit, the pedestal extends into a pedestal opening in a sub-floor of the unit. The first electrode array-facing walls of the pedestal opening urge the arms and the strip on each arm to pivot upwardly, from a horizontal to a vertical disposition. This configuration can improve resistance between the electrode arrays.
Yet another embodiment provides a cleaning mechanism for the wires in the first electrode array in which one or more bead-like members surrounds each wire, the wire electrode passing through a channel in the bead. When the transporter-conditioner unit is inverted, top-for-bottom and then bottom-for-top, the beads slide the length of the wire they surround, scraping off debris in the process. The beads embodiments may be combined with any or all of the various sheets embodiments to provide mechanisms allowing a user to safely clean the wire electrodes in the first electrode array in a transporter-conditioner unit.
Other features and advantages of the invention will appear from the following description in which the preferred embodiments have been set forth in detail, in conjunction with the accompanying drawings.